1. Field of the Invention
The present invention relates generally to data communication equipment, and more particularly, to a gateway, which can enable mutual data transmission between a plurality of networks by connecting the networks.
2. Description of the Related Art
Among equipment required in data communication, a gateway functions as a gate of a network, and enables transmission of data by connecting different kinds of networks. Functions of such a gateway are described with reference to FIG. 1. FIG. 1 is a view showing the construction of two networks connected to each other through a conventional gateway.
As shown in FIG. 1, a first local area network (LAN) 112 and a second LAN 114, which are independent networks, are connected to each other through a gateway 102. The first and second LANs 112 and 114 transmit data using Ethernet based transmission control protocol/Internet protocol (TCP/IP) communication protocols. The gateway 102 is used for the purpose of data transmission between the two networks. Referring to FIG. 1, the first LAN 112 is connected to a server 104 and a host computer 106, and the second LAN 114 is connected to a main frame 108 and a single channel access device 110. The gateway 102 connects the first and second LANs 112 and 114 physically separated from each other, thus enabling data transmission between devices connected to respective networks.
The single channel access device 110 carries out its given duties by communicating with the server 104 or the host computer 106 connected to the first LAN 112 through the gateway 102. In this case, since only one communication channel is formed, the single channel access device 110 cannot simultaneously communicate with two computers, etc. Typically, the server 104 or the host computer 106 monitors operating states of the single channel access device 110, and collects data or transmits required control instructions from/to the single channel access device 110.
However, if networks are connected through the conventional gateway, the gateway 102 cannot support a normal communication mode when the gateway 102 is turned off due to logical errors, a power supply is interrupted due to power failure, a presence of unacceptable noise components/level on the supplied power, etc. Therefore, in case of gateway failure/malfunction, communication between networks cannot be carried out.
For example, the single channel access device 110 cannot communicate with the server 104 or the host computer 106, so the single channel access device 110 cannot assure normal operations. In such a case, if the single channel access device 110 cannot be normally controlled by the server 104 or the host computer 106 to perform normal operations, other entire systems related to the single channel access device 110 may be paralyzed, or may cause errors in the other systems, thus resulting in serious problems. For example, if the single channel access device 110 is a device constituting a production line of products, and the gateway 102 fails/malfunctions as described above, errors may occur in the product production process, thus greatly increasing defective production of products. Further, if the single channel access device 110 is an electric power generation device or a device of a chemical plant, etc., and failures/malfunctions as described above are generated, the failures/malfunctions may cause fatal accidents, thereby possibly causing/increasing risks of significant loss of lives.